186SL0798131036901 191A 19670511 19670831 1614S 03954E 2 00000R 0000 MM 186SL0798231036901 Antonio Enes Mozambique Inst. Hidro. Marinha 186SL079830001 186SL079830002 QUALITY ASSESSMENT OF SEA LEVEL DATA 186SL079830003 by the 186SL079830004 TOGA SEA LEVEL CENTER/NATIONAL OCEANOGRAPHIC DATA CENTER 186SL079830005 JOINT ARCHIVE FOR SEA LEVEL 186SL079830006 186SL079830007Station : Antonio Enes Latitude: 16 13.9S 186SL079830008Country : Mozambique Longitude: 039 54.1E 186SL079830009JASL # : 191A Time Meridian: 030E (GMT + 2 hr) 186SL079830010GLOSS # : none TOGA #: none NODC #: 31036901 186SL079830011Contributor : Instituto Hidrografico Marinha 186SL079830012 Rua das Trinas 186SL079830013 49-P-1296 Lisboa Codex 186SL079830014 Lisbon, Portugal 186SL079830015Originator : same 186SL079830016Original Data: unconfirmed 186SL079830017Instrmnt Type: unconfirmed 186SL079830018Digitzd Intvl: unconfirmed 186SL079830019Present Data : Hourly, daily, and monthly values obtained by: 186SL079830020 Hourly : unconfirmed 186SL079830021 Daily : 119-point convolution filter (Bloomfield, 1976) 186SL079830022 centered on noon applied to the hourly data 186SL079830023 with respective periods of the 95, 50, and 5% 186SL079830024 amplitude points at 124.0, 60.2, and 40.2 hours 186SL079830025 Monthly: Simple average of all daily values; calculated if 186SL079830026 7 or fewer days are missing 186SL079830027Span of data : 11 May 1967 - 31 Aug 1967 186SL079830028Gaps > 1 mon : none 186SL079830029Time Refernce: GMT (hours 00-23) Space-filler Flag :-9999 186SL079830030Units : millimeters Missing Data Flag :99999 186SL079830031Refernce Levl: All heights have been referred to the station tide 186SL079830032 staff zero which is linked to fixed bench marks 186SL079830033Comment : The daily means due not reveal any obvious 186SL079830034 reference level problems. Timing errors occur 186SL079830035 throughout. 186SL079830036 186SL079830037 CI MISSING REPLACED GAPS QUESTIONABLE 186SL079830038YEAR (%) DATA OR BAD DATA FLUCTUATIONS 186SL079830039---- --- -------------------- --------------- -------------------- 186SL0798300401967 31 none none 131-243 186SL079830041 186SL079830042 QUALITY ASSESSMENT POLICY 186SL079830043 186SL079830044 The quality assessment is mostly based on the residuals 186SL079830045 (observed data minus predicted tides) of the hourly data. This 186SL079830046 assessment also applies to the daily and monthly data since 186SL079830047 they were derived from the quality-controlled hourly data. 186SL079830048 186SL079830049 The following abbreviations are used in the assessment: 186SL079830050 JASL - Joint Archive for Sea Level; GLOSS - Global Sea Level 186SL079830051 Observing System; TOGA - Tropical Ocean Global Atmosphere 186SL079830052 research program; NODC - National Oceanographic Data Center; 186SL079830053 Instrmnt - instrument; Digitzd Intvl - digitized interval; 186SL079830054 Gaps > 1 mon - missing data in a span greater than one month; 186SL079830055 Refernce - reference. 186SL079830056 186SL079830057 The following corrections are made to the hourly data 186SL079830058 prior to this assessment: 186SL079830059 1) Gaps or obviously wrong data points in a span less than 186SL079830060 25 hours are filled by the predicted tide method*. 186SL079830061 2) Timing errors of exact increments of an hour are corrected 186SL079830062 by shifting the data. 186SL079830063 3) Reference level shifts are only corrected after information 186SL079830064 from tide staff readings or comparative readings with a fixed 186SL079830065 bench mark are checked to verify that the shift was not a 186SL079830066 natural event. If comparative readings are missing or 186SL079830067 incomplete, comparisons of the data with nearby stations 186SL079830068 may warrant the adjustment of some obvious shifts. 186SL079830069 4) Data with unresolved datum shifts are not disseminated. 186SL079830070 However, if sufficient time spans of data are available before 186SL079830071 or after the year(s) with the unresolved shift(s), a subset of 186SL079830072 quality assured data is made available. Thus, the Span field 186SL079830073 in the Quality Assessment may not match the span of the 186SL079830074 distribution data set. As the questionable datum shifts are 186SL079830075 resolved, the data set will be updated. Although this policy 186SL079830076 adds some complexity, it allows more rapid dissemination of 186SL079830077 at least the quality assured years. 186SL079830078 186SL079830079 For each year, the following information is documented from 186SL079830080 the quality-controlled hourly data with dates given as the nth 186SL079830081 day of the year starting from 1 January: 186SL079830082 1) a Completeness Index (CI) based on the percentage of hours 186SL079830083 with available data, 186SL079830084 2) a list of gaps longer than a day, 186SL079830085 3) a summary of days with consecutive missing or obviously 186SL079830086 wrong data in a time span longer than 6 but less than 25 186SL079830087 hours that have been replaced, with hours in parentheses, and 186SL079830088 4) a summary of days with questionable fluctuations in the 186SL079830089 residual series. Fluctuations within the residuals are 186SL079830090 considered significant and are noted if they are greater than 186SL079830091 25 cm. This policy has changed slightly as of October 1992: 186SL079830092 only suspicious fluctuations due to obvious instrumentation 186SL079830093 problems are noted. Minor timing drifts are no longer 186SL079830094 included in the list of questionable days. 186SL079830095 186SL079830096 Note : If the predicted tides poorly model the observed heights 186SL079830097 due to the inability of the tidal analysis to completely resolv 186SL079830098 the non-linear shallow water effects, the residuals are not 186SL079830099 suitable for assessing the data quality. Instead, a subjective 186SL079830100 comment on the quality of the data is provided. 186SL079830101 186SL079830102 *The predicted tides are obtained with the use of a harmonic 186SL079830103 analysis program (Foreman, 1977) which is executed on a year 186SL079830104 of apparently good data for a given station. The Predicted 186SL079830105 Tide Method for filling gaps consists of statistically 186SL079830106 comparing the predicted tides to the observed data and 186SL079830107 shifting the predicted tides in time to correct for timing 186SL079830108 differences. Then the linear interpolation between hourly 186SL079830109 values at the end points of the gap in the residual series is 186SL079830110 added to the corresponding corrected predicted tide data to 186SL079830111 obtain interpolated values over the span of the gap. 186SL079830112 186SL079830113 Bloomfield, P., 1976. Fourier Analysis of Time Series: An 186SL079830114 Introduction. New York: John Wiley and Sons. pp 129-137. 186SL079830115 186SL079830116 Foreman, M., 1977. Manual For Tidal Height Analysis and 186SL079830117 Prediction. Institute of Ocean Sciences, Patricia Bay, 186SL079830118 Victoria B.C. Pacific Marine Science Report 77-10. 186SL079830119 186SL07986 19671 9999999999999999999999999999999999999999 5079000 186SL07986 19672 5054000 508601099999999999999999999999999999999